The BlackBerry-tethered tablet can't do very much, and its tethering requirement means few users can actually use it

It's been half a year since Research in Motion unveiled its BlackBerry PlayBook tablet based on the QNX operating system. This week, RIM began shipping the 7-inch tablet. After spending a couple days with the final product, it's clear that the PlayBook is a useless device whose development is unfinished.

Not only can it not compete with an Apple iPad, it can't compete with the second-best tablet, Motorola Xoom, nor even with marginal Android tablets such as the Galaxy Tab that use the smartphone version of the Android OS rather than the Honeycomb tablet version. In fact, if my choice were between a PlayBook and a Windows 7 tablet -- my benchmark for unusability -- I think I'd rather go sans tablet.

I knew the prerelease reviews were negative, and I had my own concerns after seeing a PlayBook demo in January. But even those didn't prepare me for the profound disappointment that is the PlayBook. Why did RIM bother shipping it?

Communications only if the straitjacket fitsThe fundamental nature of the PlayBook's flaws begin with the requirement that a BlackBerry be tethered to it for access to business email, calendars, or contacts. Other than using a Webmail client, a PlayBook without a BlackBerry is unable to communicate. You can't connect to POP, IMAP, or Exchange servers directly from the tablet, as you can from an iOS or Android device -- you must have a BlackBerry tethered via Bluetooth using the BlackBerry Bridge application. In that case, you essentially see your BlackBerry email, calendar, and contacts in a window on the PlayBook when connected.

If your BlackBerry is on the AT&T network, you can't install Bridge -- AT&T won't allow it. As luck would have it, my BlackBerry Torch uses the AT&T network, so AT&T blocked me from installing Bridge, which meant I could not get my Exchange or IMAP email, work with my calendar, or look up contacts. It also meant I couldn't use mailto links in the browser, such as in "share with a friend" links -- extremely frustrating. This is what happens when you lock in customers before making sure your business partners (AT&T, in this case) will support your particular type of straitjacket. (And note that Verizon Wireless hasn't yet decided whether it will support the PlayBook.)

Companies that don't use BlackBerry smartphones will be in the same position as AT&T-provisioned BlackBerry device users like me: The PlayBook will not be viable for business communications. Webmail is a poor substitute for native email.